1. Technical Field
This disclosure generally relates to wafer manufacturing, such as wafer manufacturing involving thin film deposition.
2. Background Art
Semiconductor manufacturing, like many types of manufacturing, strives to produce more products faster and at higher quality. Over the years, semiconductor manufacturing has become highly automated and is performed in a series of photolithographic and chemical processing steps. These steps can generally be categorized as wafer processing, die preparation, integrated circuit (IC) packaging and IC testing. Of particular relevance is the step of chemical vapor deposition (CVD) or atomic layer deposition (ALD), which is part of wafer processing.
CVD and ALD are often used to create a thin film on a semiconductor wafer. A gas precursor, often two gas precursors, are released above the substrate surface of the wafer to decompose and/or react on the surface. A growth film can be created by repeatedly exposing the surface to the volatile precursors. With ALD, a purge gas is usually injected between applications of reactant to force the reactive precursor (and/or any byproducts) out of the reaction chamber to ensure nothing unexpected remains in the chamber prior to the next reaction.
Wafers may be processed one at a time or in a batch process. The term single wafer processing generally means that only one wafer at a time is processed at a given step; the term does not typically mean that only one wafer is being manufactured at a time. In contrast, batch processing can be beneficial when one is looking to produce a large number of identical wafers, perhaps for a computer chip to be sold to the general public, such as for a graphics card or a central processing unit. However, batch processing may impose additional constraints, such as the need for parallel machinery to process all of the wafers during a given step.
Wafer manufacturing is concerned with producing results that are uniform and repeatable. This is particularly true for batch manufacturing, because higher volumes are being manufactured and a lack of uniformity may lead to a reduced yield, lowered specifications (to allow for higher variability in manufacturing), and difficulty in ramping up production. Because annual sales of semiconductor chips have risen to $200-300 billion per year and continue to grow, even small improvements to manufacturing uniformity can be quite valuable.
Therefore, a need exists for improved processing of wafers.